Art of converting hydrocarbons



Oct. 24, 1950 D. B. ARDERN ART OF CONVERTING HYDROCARBONS 2 Sheets-Sheet 1 Filed May 25, 1948 Oct. 24, 1950 D. B. ARDERN 2,526,625

ART OF CONVERTING HYDROCARBONS 2 Sheets-Sheet 2 Snventor I fldVid B. Arden:

tion zone and a lower disengaging zone.

, desired entrainment of catalyst in Patented Oct. 24, 1950 7 ART OF CONVERTING HYDROCARBONS David B. Ardern, Moylan, Pa., assignor to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware Application May 25, aser-m1 No. 29,007

6 Claims. (01. 196 -52) My invention relates to the art of convertin hydrocarbon material.

In a knownsystem for cracking or otherwise converting hydrocarbons, small pieces of catalytic material gravitate in solid 'bed fashion through a housing defining an upper conversion or reac- As this operation proceeds, hydrocarbon material traverses the conversion zone in concurrent relation as regards the gravitating catalyst and, in the disengaging Zone, the converted vapors are disengaged from the catalyst and thereafter passed from the aforesaid housing. Simultaneously, spent catalyst passes from the conversion housing and then traverses another housing wherein the catalyst is regenerated, the regenerated catalyst being returned to said conversion housing for further use in the manner described. 1 -If, in a system of the-general character re! ferred to above, the ratio of catalystto hydrocarbon. material (catalystatoroihratio) is irrsubstantially transverse area, is defined by spaced members such, for example, as inverted cup-shaped members or inverted channel members, a plurality of which are disposed at each of a plurality of" different levels and utilized for deflectin the gravitating catalyst whereby, beneath each member, there is formed a catalyst surface facing generally upwardly from which converted vapors are disengaged. If the horizontal and vertical dimensions of said disengaging zone together with the number of the therein-contained catalystdeflecting members are. properly selected, the velocity of the converted vapors leaving each of the aforesaid catalyst surfaces is maintained at such low magnitude that undesired entrainment of pieces of catalyst in these vapors is insubstantial.

When, in the conversion system described below, the space rate of the hydrocarbon material is increased compared with prior practice as referred to above, the quantity of catalyst which, necessarily, is constantly maintained in the aforesaiddisengaging zone is at least approximately equal to. the quantity ofcatalyst which, necessarily, is constantly maintained: in the con-version zone to insure completion'of the conversion operation to the extent desired. Un-

favorable distribution of converted products,the 1 space rate or spacevelocity of thehydrocarbonmaterial- (pounds of hydrocarbon material supplied to the. conversionzone per hour for each pound of catalyst present therein) maybe increased to marked extentcompared with prior practice by substantially decreasing the volume of catalyst in the conversion zone. However; it is necessary for the conversion zone to. constantly contain suificient catalyst to insure substantial completion of the hydrocarbon conversion operation upon arrival of the concurrently flowing vapors at the bottom level of said conversion zone although, as will be understood, additional conversion occurs in a disengaging zone-of the character hereinafter described. It is also necessary for the total area of the disengaging SUI, faces in the disengaging zone to be sufficient for maintaining the vapors, as they leave said disengaging surfaces, at such low velocity that unthe disengaging zone thereof, throughout its these vapors v der. .this condition, it has been ascertained,, if

the transverse areaof the conversion zone is the "concurrently through the conversion zone is insuflicient to maintain the desired vapor flow therethrough in the event that an abnormal con-' dition develops in the disengaging zone as hereafter described. In order to overcome this defect and in accordance with the invention, the transverse. area of said conversion zone compared with that of said disengaging zone is suitably restricted so that, with the resultant de-, crease in transverse area and increase in height of thatzone, the pressure drop of the hydrocarbon, vapors passing concurrently therethrough substantially exceeds the pressure drop of said vapors during subsequent passage I thereof through and from said disengaging zone. This is highly desirable for the reasons hereinafter stated. I

-';V-arious other objects and advantages of my inventionr will become apparent from "the following detailed description.

My invention resides in the-,a'rtof converting hydrocarbon material, the method and features of the character hereinafter described and claimed.

For an understanding of my invention and for an illustration of one form of apparatus with which the invention may be practiced, reference is to be had to the accompanying drawings, in which:

Fig. 1 is an elevational view, partly in section and partly broken away, showing apparatus constructed and arranged-in accordance with the invention; a I

Fig. 2 is a horizontal sectional view, partly in plan, taken on the line 2-2 of Fig. 1; 1i

Fig. 3 is an enlarged elevational view, partly in section, showing a part of the disengaging zone illustrated in Fig. l and is taken on the line 3-3 of Fig. 4; v

Fig. 4 is a horizontal sectional view, partly in plan, taken on the line 44 of Fig. 3;

Fig. 5 is an enlarged elevational view, partly in a section, showing a vapor-disengaging tube and:

associated cup-shaped members; and

Fig. 6 is a horizontal sectional view, partly in plan, taken on the line 66 of Fig. l.

Referring to Fig. 1, I have shown a vertical housing I which, in horizontal section, may be circular or of any other suitable configuration. Interiorly of the housing 6, there is a conversion or reaction zone R whe'reinhydrocarbon material is cracked or otherwise converted in the pres-, ence of small pieces of catalyst C which move downwardly therethrough under the influence of gravity, the catalyst C being introduced into said housing I in suitable manner, as by an inlet pipe 2 extending through the top housing wall at the center thereof.

Inthe form of the invention herein shown, although not necessarily, a shallow receptacledike member 3 is suitably supported in the upper portion of the housing l The catalyst is admitted to the member 3 by the inlet pipe 2 and it may be discharged 'therefrom in suitable manner, as by Y pipes 4 which open throughj and depend from said member 3; If desired, there may be a central piped and other pipes 4 disposed in circular rows arranged in concentric relation with respect to the housing I and spaced to substantial extent from the interior surface thereof, the

gager assembly comprises a horizontal tube sheet 6 which is welded to or otherwise suitably supported by the interior surface of the housing I. The tube sheet 6 supports a plurality of vertical tubes 7 which open therethrough and extend upwardly therefrom, each tube 1 having secured thereto a plurality of spaced frusto-conical or inverted cup-shaped members 8, sets of. which are disposed at different respective levels as indicated. As clearly appears from a consideration iOf Figs. 1, 3 and 4, linear rows of the tubes l and the cup-shaped members 8 in adjacent rows being disposed in staggered relation. As referred to in this specification, the disengaging zone D extends upwardly'from the lower surfaces of the respective'cup-shaped members defining the lower level thereof and terminates at the upper surfaces of therespective tubes l.

Referring particularly to Fig. 5, one of the tubes 1 is shown as comprising a passage la for each cup-shaped member 8 carried thereby, each passage 7a opening into the space defined by the associated cup-shaped member well above the lower surface thereof. For a purpose hereinafter stated, the areas of the respective passages la progressively increase ina direction extending from the top of the tube 1 toward the bottom thereof. As regards each of the other tubes I, it shall be understood that the respective areas of its passages 1a correspond with the tube passage areas shown in Fig. 5.

Referring further to Figs. 1 and 3, the aforesaid tube sheet 6 is shown as supporting a plurality of vertical pipes 9 which open therethrough and depend therefrom, the pipes 9 being utilizable as hereinafter described.

Below the disengager assembly described above, a second horizontal tube sheet ii! is welded to or otherwise suitably supported by the interior surface of the housing Opening through the tube sheet 10 and depending therefrom are a plurality of vertical pipes I I. The diameter of each pipe '5 l is substantially greater than that of each pipe 9, the pipes I i being utilizable as hereinafter described.

When hydrocarbon material'is to be cracked in the conversion zone B of the housing I, the cata' lytic material C hereinbefore'referred to may respectively, converge and diverge in a downward direction. Preferably, the throat of the member 5 as ind cated at 50 coincides, approximately, with the aforesaid horizontal plane defined by the lower ends of the pipes 5 and, hence, the portion 512 of the member 5 defines the aforesaid conversion zone B.

Further in accordance with the invention, the housing I defines a disengaging zone D within which a disengager' assembly is disposed and,

preferably the top surface of this assembly cointrated, it is 'constructedgenerally in accordance 1' with the disclosure of the pending application of James E. Evans, erial -No 682,463, filed July 10,

As shown in Figs 1 and 3, the aforesaid d senhave average temperature, while in"saidzone R, of about 900 F. or higher. Any suitable'kind of catalytic material may be utilized such, for ex ample, as activated clay pellets or synthetic silica-alumina pellets or beads, etc, having suitable major dimensions ranging from fines upwardly to one-quarter of an inch or more, approximately 10 mesh being a preferred size. Other suitable catalysts for cracking include synthetic plural oxide composites, silicious or nonsilicious in character, and containing, for example, zirconia, alumina or beryllia'. In lieu of a cracking operation, other types of conversion operations such, for example, as one wherein hydrocarbon material of the character referred to be low is desulphurized under known conditions with catalytic contact material of the general character referred to above, or equivalent. Or, reforming or dehydrogenation of naphthas or other normally liquid hydrocarbons may be effected in the presence of the above or other desired types of catalyst, certain of which are well known in the art.

In operation, regenerated catalyst C passes ing:zone. are disposed in groups or sets at difierent respective levels and are staggered with. respect .to each other in conformity with the. staggered relation of the cup-shaped scribed.

continuously from thepipe 2 and, to suitable extent, fills .thereceptacle 3 which defines an upper zone'of the housing I. ceptable 3,:the catalyst gravitates through the .pipes 4 which should be suitably spaced with From the rerespect to each other so as to maintain the upper surface of the catalyst bed in the conversion zone-R more or less, in level condition. Thereafter, in solid bed fashion, the catalyst gravitates through-the conversion zone R and the and thereafter leaves said housing I by way of a .,conduit l2, the rate of flow of catalyst along the path described above being controlled in any suitable manner, for example, by a valve I3.

As the foregoing operation proceeds, vaporsto becraclred such, for example, as vaporized gas oil, naphtha or lighter hydrocarbons having suitable elevated temperature are admitted continuously to the housing I by way of a conduit I4. Thesevapors pass through the conversion zonev R concurrently as regards the gravitating catalyst C and, in the presence thereof, are con- .verted to cracked products or vapors. upon, the cracked vapors-enter'the disengaging Therezone D and, while still flowing concurrently as regards the gravitating catalyst, aredisengaged ltherefrom at the lower surfaces of the respective cup-shaped members 8, the disengaged vapors thereafter entering the respective tubes 1, passing downwardly therethrough, entering the space be- .low-the tube sheet 6 and then-passing to any suitable destination by way of a conduit I5.

. -As regards the aforesaid disengaging operation,, each of the cup-shaped members 8 defines a location wherein the catalyst, while following a circumferentially complete path, is de- -flected,so asto forms, catalyst surface s beneath eachcup-shaped member 8, Fig. 5, the converted vapors being disengaged at each of these surfaces. As hereinbefore stated, linear rows of the,cupshaped members 8 extend horizontally through the disengaging zone D and,itherefore,

it necessarily follows that the aforesaid catalyst- -deflecting locations and the respective catalyst surfaces 3 associated therewith likewise extend as linear rows horizontally through said disengag- Further, these locations and surfaces members 8 as de- More particularly with respect to the. aforesaid from the. uppermost level of the cup-shaped I members 8. The passages Ia in the. uppermost level, then, throttle the downwardly flowing cracked vapors so that a desired portion of the totalquantity of said cracked vapors are disengaged at the upper level of cup-shaped mem- -bers fi. The passages 1a at the next lower level (which are slightly larger than the upper passages Ia) also exercise a throttling effect on the remaining downwardly flowing cracked vapors so that a desired'portion of the vapors last'named are disengaged at the cup-shaped material.

members 8 associated with the respective passages Ia of said next lower level. At successively lower levels of the cup-shaped members 8, the operation is as described above with respect to the two uppermost levels and, therefore, it will be understood that a desired portion of the downwardly flowing cracked vapors is disengaged at each level of said cup-shaped members, the disengaging operation being completed at the lowermost level thereof.

As the above described operation proceeds and in order to prevent passage of hydrocarbon vapors from the housing I by way of the conduit I2, a suitable purging medium such, for example, as steam or flue gases is admitted to the chamber below the tube sheet III by way of a conduit I6, Fig. 1, under pressure above that existing at the level of the outlet pipe I5. A portion of this purging medium flows downwardly through the lower end of the housing I and then passes therefrom by way of the conduit l2. The remaining portion of said purging medium passes upwardly through the pipes II, through the shallow catalyst. bed onthe tube sheet I0 and then flows from the housing I by way'of the conduit I5. When, in a system 'of the character described, the catalyst-to-oil ratio is high compared with prior practice, it necessarily results that movement of the catalyst through the housing I is accelerated compared with prior art practice. In view of this, the length of the pipes .I I and the depth of the catalyst bed on the tube sheet II! are selected so that, despite accelerated catalyst movement, the purging medium remains .renderit efiective for its intended purpose It was hereinbefore stated that the hydrocarbon vapors pass through the housing I concurrently as regards the gravitating contact In order to obtain this concurrent vapor flow, a suitable sealing medium, such as steam or flue gases, may be admitted to the top of the housing I by way of a pipe Ia,- Fig. 1, this sealing medium being maintained under pressure slightlygreater than that of said hydrocarbonvapors in order to prevent passage thereof upwardly first through the pipes 4 and then through the pipe 2. s

As regards the catalyst surfaces .9 beneath the respective cup-shaped members 8, two factors, namely, the quantity ofvapors entering the dis-- engaging zone per unit of time and the size of thepieces of catalyst are controlling as regards the total area which said catalyst surfaces s should have if the vapors are to be substantially prevented from lifting catalyst a substantial distance, namely, upwardly as far as the passages Ia. With information concerning .iese factors available and for a disengaging zonehaving a given transverse area, the total number of cup-shaped members 8 required may readily be determined after the area to be defined by the lower opening of each of said members has been computed, Obviously, information concerning the total required number of cup-shaped members is indicative of the number of superposed levels thereof which should be disposed inthe disengaging zone.

Assuming that the conditions are noted immediately above as regards the quantity of vapors entering the disengaging zone per unit of time and the number of cup-shaped members required therein in order to effect. vapor disengagement as specified, the catalyst-to-oil ratio, during operation of the system disclosed hereinma have suitable magnitude which, preferably, is relatively high compared with prior practice in the gravitating catalyst art to which this invention apertains. By suitably decreasing the quantity of catalyst in the conversion zone, five pounds of hydrocarbon material may, for example, be admitted to 'the conversion zone per hour for each pound of catalyst present therein (space rate of five). If so, it has been ascertained that the quantity of catalyst which, necessarily, is constantly maintained in the disengaging zone D (due to the dimensions thereof as imposed by the presence of the described disengaging elements) is approximately 45 of the total quantity of catalyst which is constantly maintained in both of the zones D and R.

Under the conditions noted above, if it be assumed that the transverse area of the conversion zone is the same or substantiall the same as that system of the character herein disclosed and par- I ticularly if an overload condition develops, one or more of the tube passages la may become plugged due to lo'dgment of pieces of catalyst therein. 1

Further, some of the catalyst instead of gravitating freely, forms, to some extent at least, stagnant of non-moving masses or layers at the respective lower openings of some of said cupshaped members. In addition, in the course of time, undesired erosion of some of the tube passages la may develop. Resulting from the foregoing, the pressure drop through the individual cup-shaped members which are adversely affected as noted above causes cross-flow of vapors in the disengaging zone by reason of the fact that said vapors are not uniformly distributed as regards all of the cup-shaped members. When the pressure drop ratio through the conversion and disengaging zones is in the approximate ratio of 1:1 as noted above, development of the described abnormal condition in the disengaging zone i reflected upwardl into the conversion zone in the sense that there is channelling or non-uniform distribution of the vapors passing downwardly therethrough. This, of course, is undesired because adversely affecting the conversion operation.

In order to avoid or substantially minimize this adverse conversion effect, I utilize the member 5, or equivalent, hereinbefore described and, in so doing, I substantially restrict the transverse area of the conversion zone compared with that of the disengaging zone. As a result, the height of the catalyst bed gravitating through the conversion zone is substantially increased and this together with the decreased transverse area of said conversion zone effects a corresponding substantial increase in the pressure drop in pounds per square inch of the hydrocarbon vapors passing downwardly therethrough.

For the purpose stated, the height of the catalyst bed gravitating through the conversion zone may be increased to such extent as is suitable or desirable. Thus, for example, resulting from the foregoing, the pressure drop through the conversion zone may become approximately'two and one-half times more than that through the disengaging zone. Resulting from this substantial pressure drop increase through the conversion zone, flow of hydrocarbon vapors therethrough is maintained approximately in the desired uniform relation even though abnormal conditions develop in the disengaging zone as noted above. In addition, the distribution of vapors in the disengaging zone is also improved to some extent.

For purposes of explanation and without limitation of the invention, the following detailed description is included as a part of this specification.

The housing I has interior diameter of 15 feet. In the disengaging zone, there are 428 vertical tubes 1 each having external diameter of 2% inches, these tubes being spaced in uniform relation 7% inches apart in square pattern formation. Each vertical tube 7 carries six of the cup-shaped members 8 which are secured thereto in uniform spaced relation. Each cup-shaped member has height of 3% inches and the external diameter of the opening defined by the lower surface thereof is 6 inches. Thus, the disengaging zone has internal diameter of 15 feet and the height thereof from the bottom surface of the lower level of cup-shaped members 8 to the top surface of the tubes 1 is 48 inches. When charging 27 0,000 pounds per hour of hydrocarbon material and using catalyst of 42 pounds per cubic foot apparent density, the disengaging zone D, for a space rate of 5, constantly contains approximately 581 cubic feet of catalyst. Either with or without the member 5, the conversion zone R constantly contains approximately 696 cubic feet of catalyst. Accordingly, the quantity of catalyst which is constantly maintained in the disengaging zone is approximately 45% of the quantity which is constantly maintained in the conversion zone R and in the disengaging zone D. It shall be understood that claim language reading whereby the volume of catalyst in said diseniga'ging zone is necessarily approximately at least one half of the total volume of catalyst present in said confined zone (which confined zone includes both zones R and D) shall be interpreted as including the percentage figure of 45 noted above.

In the absence of the member 5, the diameter of said conversion zone R is 15 feet and the depth of the bed therein is approximately 46% inches. The pressure drop of the hydrocarbon vapors through such a conversion zone is approximately 1.7 pounds per square inch whereas the pressure drop of said vapors through the disengaging zone is approximately 1.6 pounds per square inch. When the member 5 is utilized and, if the portion thereof defining the conversion zone, is related to a horizontal plane by an angle of approximately '70 degrees, the depth of the bed in said conversion zone becomes approximately 63% inches. For this decreased transverse area and increased height of the conversion zone, the pressure drop of the hydrocarbon vapors passing therethrough is approximately 4.1 pounds per square inch.

This exceeds the pressure drop through the disengaging zone as noted immediately above to such substantial extent that flow of hydrocarbon vapors through both'zones is effectively maintained even though operation of the disengaging members should be adversely affected as noted above.

In the event that the space rate is increased 5, or equivalent,'having proper'diametenthepressure drop of the hydrocarbon'vapors through the conversion zone is substantially increased compared with the pressure drop ofsai'd' vapors through the disengaging zone, this being highly desirable for the reasons hereinbefore stated. It will be understood that, when the space rate is increased to substantial extent above 5, the pressure drop relation referred to above is not as favorable as hereinbefore described for a space rate of 5. However, even so, utilization of said member 5, or equivalent, is advantageous because definitely improving an otherwise unfavorable pressure drop relation.

It is to be understood that there is to be no limitation of my invention to utilization of the hereinbefore described member 5. Obviously, the transverse area of the conversion zone R may be restricted otherwise than by utilization of said member 5. Thus, for example, the conversion zone may be defined by a tubular member having, throughout the height thereof, uniform crosssectional area which, however, is less to a desired degree than that of the disengaging zone D.

The invention has been hereinbefore described with respect to the conversion of hydrocarbon vapors which are admitted to the housing I by preferably a large proportion, of liquid hydrocarbon material such, for example, as a suitable residual stock, topped or reduced crude having temperature elevated into a suitable range as, for example, from 250 F. to 800 F. After admission to the housing l, the liquid hydrocarbon material may be engaged with the catalyst in any suitable manner.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated inthe appended claims.

I claim as my invention:

1. In a process for cracking hydrocarbons wherein hydrocarbon vapors contact a downwardly moving compact bed of fluent granular solid hydrocarbon conversion catalyst in a confined zone, the steps which comprise passing said catalyst downwardly in said zone as a solid bed whose horizontal cross sectional area increases to a maximum, passing hydrocarbon vapors downwardly through said bed at space velocities of at least pounds of hydrocarbons passed through said zone per-hour per pound of catalyst therein, passing catalyst from said bed downwardly through a disengaging zone located in said confined zone below and contiguous with the bottom of said bed while bafiiing the flow of catalyst in said disengaging zone at each .of a plurality of regularly horizontally arranged locations in each of a plurality of vertically separated levels with the resultant formation of a plurality of surfaces at each of said vertical levels, the total area of said disengaging surfaces being great enough 'that the hydrocarbonvapors passed through said bed are" disengaged from the cataly'st'at "velocitiesf below thevel o'qity at which said catalystiis' lifted"from the 'dieeng ging surface whereby the volil'rr'ie bffcatalyst"in said disengaging zone is necessarily 'a'pproxi mately at least'half of the total volume of catalyst present'in said confined zone, d: charging catalyst from the bottom of said disengaging zone, disengagingcracked hydrocarbpn vapors from catalyst at said disengagingsi-irfacesand passing disengaged hydrocarbon vapors through restricted openings to a location outside said confined zone, the average area of said bed being so related to the size of said restricted openings that the pressure drop of hydrocarbon vapors passing concurrently through the bed substantially exceeds the pressure drop of said vapors during subsequent passage thereof through and out of said disengaging zone.

2. The method of claim 1 wherein the pressure drop of the vapors passing through the bed is more than about twice the pressure drop of the vapors passing through and out of the disengaging zone.

3. The method of claim 1 wherein the bottom of said bed has a horizontal cross sectional area substantially the same as the top of a disengaging zone having constant horizontal cross sectional area and'wherein said bed has a downwardly diverging frusto-c'onical shape, the plane of the side'of said frusto-conioal shape forming an angle of about 70 with the horizontal.

4. The method of claim 1 in which at least a portion of the hydrocarbon vapors are derived from liquid hydrocarbon material which has contacted hot catalyst in the upperportion of said confined zone.

, 5. In a process for cracking hydrocarbons wherein hydrocarbon vapors contact a downwardly moving compact bed of fluent granular solid hydrocarbon conversion catalyst in a confined zone, the steps which comprise passing said catalyst downwardly in said zone as a solid bed whose horizontal cross sectional area gradually increases to a maximum, passing hydrocarbon vapors downwardly through said bed at space velocities of at least 5 pounds of hydrocarbons passed through said zone per hour per pound of catalyst therein, passing catalyst from said bed downwardly through a disengaging zone located in said confined zone below and contiguous with the bottom of said bed while bafiling the fiow of catalyst in said disengaging zone at each of a plurality of regularly horizontally arranged locations in each of a plurality of vertically separated-levels with the resultant formation of a plurality of surfaces at each of said vertical levels, the total area of said disengaging surfaces being great enough that the hydrocarbon vapors passed through said bed are disengaged from the catalyst at velocities below the lifting velocity of said catalyst whereby the volume of catalyst in said disengaging zone is necessarily approximately at least half of the total volume of catalyst present in said confined zone, discharging catalyst from the bottom of said disengaging zone at a plurality of points regularly arranged over the horizontal area of the bottom of said disengaging zone, disengaging cracked hydrocarbon vapors from catalyst at said disengaging surfaces and passing disengaged hydrocarbon vapors through restricted openings to a location outside said confined zone, the average area of said bed being so related to th size of said restricted openings that the pressure drop of hydrocarbon vapors passing concurrently through the bed substantially exceeds the pressure drop of said vapors during subsequent passage thereof through and out of said disengaging zone.

6. The method of claim 5 wherein said bed has a diverging frusto-conical shape and wherein the pressure drop of vapors passing through the bed is more than twice the pressure drop of the vapors passing through and out of the 10 disengaging zone.

DAVID B. ARDERN.

12 REFERENCES CITED 'ihe following references are of record in. the file of this patent:

UNITED STATES PATENTS Number Name Date 2,393,227 Anderson Jan. 22, 1946 2,439,348 Simpson et a1 Apr. 6, 1948 2,445,092 Utterback July 13, 1948 OTHER REFERENCES Houdry Pioneer, vol. 2, No. 1, Oct. 1946, Fig. '3 only. i 

1. IN A PROCESS FOR CRACKING HYDROCARBONS WHEREIN HYDROCARBON VAPORS CONTACT A DOWNWARDLY MOVING COMPACT BED OF FLUENT GRANULAR SOLID HYDROCARBON CONVERSION CATALYST IN A CONFINED ZONE, THE STEPS WHICH COMPRISE PASSING SAID CATALYST DOWNWARDLY IN SAID ZONE AS A SOLID BED WHOSE HORIZONTAL CR4OSS SECTIONAL AREA INCREASES TO A MAXIMUM, PASSING HYDROCARBON VAPORS DOWNWARDLY THROUGH SAID BED AT SPACE VELOCITIES OF AT LEAST 5 POUNDS OF HYDROCARBONS PASSED THROUGH SAID ZONE PER HOUR PER POUND OF CATALYST THEREIN, PASSING CATALYST FROM SAID BED DOWNWARDLY THROUGH A DISENGAGING ZONE LOCATED IN SAID CONFINED ZONE BELOW AND CONTIGUOUS WITH THE BOTTOM OF SAID BED WHILE BAFFLING THE FLOW OF CATALYST IN SAID DISENGAGING ZONE AT EACH OF A PLURALITY OF REGULARLY HORIZONTALLY ARRANGED LOCATIONS IN EACH OF A PLURALITY OF VERTICALLY SEPARATED LEVELS WITH THE RESULTANT FORMATION OF A PLURALITY OF SURFACES AT EACH OF SAID VERTICAL LEVELS, THE TOAL AREA OF SAID DISENGAGING SUFACES BEING GREAT ENOUGH THAT THE HYDROCARBON VAPORS PASSED THROUGH SAID BED ARE DIENGAGED FROM THE CATALYST AT VELOCITIES BELOW THE VELOCITY AT WHICH SAID CATALYST IS LIFTED FROM THE DISENGAGING SURFACE WHEREBY THE VOLUME OF CATALYST IN SAID DISENGAGING ZONE IS NECESSARILY APPROXIMATELY AT LEAST HALF OF THE TOAL VOLUME OF CATALYST PRESENT IN SAID CONFINED ZONE, DISCHARGING CATALYST FROM THE BOTTOM OF SAID DISENGAGING ZONE, DIENGAGING CRACKED HYDROCARBON VAPORS FROM CATALYST AT SAID DISENGAGING SURFACES AND PASSING DISENGAGED HYDROCARBON VAPORS THROUGH RESTRICTED OPENINGS TO A LOCATION OUTSIDE SAID CONFINED ZONE, THE AVERAGE ARE OF SAID BED BEING SO RELATED TO THE SIZE OF SAID RESTRICTED OPENINGS THAT THE PRESSURE DROP OF HYDROCARBON VAPORS PASSING CONCURRENTLY THROUGH THE BED SUBSTANTIALLY EXCEEDS THE PRESSURE DROP OF SAID VAPORS DURING SUBSEQUENT PASSAGE THEREOF THROUGH AND OUT OF SAID DISENGAGING ZONE. 